The profiler works almost like the Explain Plan tool in SQL Developer. Enter the text you want to profile, press a key and then view the output.

You do need access to the trace files that are generated. The page linked above had instructions on how to enable access and what permissions you need.

A neat feature is that you can save profiling sessions for historical access. That can be a life saver if you are trying to tune and are trying out different approaches. Instead of keeping your own backups, use the history. You can also share that history so that all of you developers have the same baseline. Nice.

Hotsos also provides a discussion group for questions relating to the extension. If you are a Hotsos profiler user, you should check out this extension.